Without limiting the scope of the invention, its background is described in connection with existing isolation and uses of reparative cell populations including preadipocytes, fibroblasts, pluripotent stem cells, endothelial cells, endothelial progenitor cells, and other supporting cell types. Isolated, or purified cell populations, have been shown to have various potential therapeutic applications. Preadipocytes may provide a durable filler for wrinkles or other cosmetic skin defects, fibroblasts may have utility to treat wrinkles and skin wounds, endothelial cells and endothelial progenitor cells may contribute to neovascularization supplying oxygenated blood to ischemic tissue, and pluripotent stem cells, due to their ability to differentiate into various cell types and tissues, may have the capacity to treat a number of conditions.
Mesenchymal stromal cells (MSC), originally isolated from bone marrow, are considered to be pluripotent and are thus potentially able to differentiate into a myriad of cell types including osteoblasts, chondrocytes, myocytes, adipocytes, and islet cells. More recently it has been found that MSC can also be isolated from the stroma of adipose tissue, which is considerably more readily obtained than is bone marrow. Indeed, by virtue of its relatively high content of MSCs, adipose tissue has been shown to be a convenient source of cells that have shown utility for cell therapy, at least in a research setting. Like MSC from bone marrow, adipose derived MSC, or “ADSC” are pluripotent. ADSC have recently yielded cell preparations useful for the repair of articular cartilage. Additionally, these stromal cells have been cultured to differentiate into cells having neuronal characteristics. Finally, ADSC have been used as a source in generating hematopoietic cells, osteogenic cells, endothelial cells, adipocytes and myocytes of skeletal and smooth muscle.
In addition to ADSC, adipose tissue is also a rich source of other cell types that may have utility in treatment of various medical conditions. Adipose tissue is a rich source of preadipocytes, fibroblasts, endothelial cells, and endothelial progenitor cells. While existing methods have allowed considerable study of isolated therapeutic cells in research environments, methods and apparatus for isolation in sufficient quantity and quality for clinical use have been problematic and continue to represent an unmet need. For example, current methods used in cell isolation and purification frequently use cell culturing. The required use of cell culturing is fairly impractical in a clinical setting wherein one might desire a rapid source of fresh cells that have a clinically useful composition. Cell sorting techniques using flow cytometry in conjunction with fluorescence tagging or magnetic affinity are also currently used and enable the isolation of cell subpopulations of good homogeneity, but these approaches are slow and impractical for obtaining large, useful cell preparations for tissue repair in a reasonable time scale. Many separation technologies also require centrifugation equipment further adding to the complexity of the process as well as increasing capital investment cost.
Devices for isolation of particular cell populations from adipose tissue have been previously described. Alchas et. al. described a device and method for collecting and processing fat tissue and procuring microvessel endothelial cells in U.S. Pat. No. 5,372,945 and an endothelial cell procurement and deposition kit in U.S. Pat. No. 5,035,708. Hu et. al. described a microvessel cell isolation apparatus in U.S. Pat. No. 5,409,833. The devices described by Alchas et al. and Hu et al. were designed to specifically isolate microvessel endothelial cells. Katz et al described adipose tissue dissociating systems and methods in U.S. Pat. Nos. 5,786,207 and 6,316,247. Fraser et al. disclosed systems and methods for separating and concentrating regenerative cells from adipose tissue in U.S. Pat. No. 7,390,484. These devices all incorporate centrifugation in the process of separating non-adipocyte cells from lipid filled adipocytes.
The use of cell preparations for therapeutic application, such as tissue repair, may be complicated by the presence of other cell types depending on the medical application. For example, the presence of leukocytes may cause immune system inflammatory problems in certain indications. This could be life threatening when the cell preparation is used in tissue repair in the heart, for example. Likewise, it may be desirable to remove erythrocytes to avoid problems related to incompatible blood group types or their involvement in thrombus formation.
In light of the foregoing, it would be beneficial to develop a system for isolating and purifying cell populations in good yields in clinical settings, which require isolation in a relatively rapid time frame. Such a system would benefit from flexibility in components to address the need for different cell subpopulations according to medical application which may span from life threatening ischemic events to cosmetic surgery. The introduction and acceptance of such new technologies into clinical practice is dependent on their cost effectiveness, safety, and ease of use.
The present invention provides several important advantages over existing technology. First, the present invention provide for a simple method to efficiently separate the non-adipocyte cell fraction from the significant fraction of lipid-filled adipocytes and oil present in a cell mixture that results from disaggregated adipose tissue or lipoaspirate. This improvement reduces complexity and capital equipment requirements. Second, the present invention offers the end user a simplified form factor such as a uniform cylinder that can be easily integrated with typical lipoaspiration equipment in clinical use. The present invention has been shown to be particularly effective in rapid and efficient isolation of desirable cell populations for use as autografts in target tissues.